1. Technical Field
The present invention relates to the fluid dynamic bearing motor.
2. Description of the Related Art
Generally, the motor used for a precise machinery like a hard disk driver requires not only high-speed driving force but also precision control. The motor, which has this character, has to support the force of the rotation load and the rotation axis, a fluid dynamic bearing motor is a recent trend to support the force instead of a metal bearing or a ball bearing.
The fluid dynamic bearing motor needs fluid for supporting rotary body, and the rotation axis of the fluid dynamic bearing motor must be positioned at the center of the sleeve for minimizing the frictional force.
The fluid dynamic bearing motor minimizes the frictional force by forming a thin oil film between the rotary body and fixed body, and that makes pressure to support the rotary body. In order to form the pressure for forming the oil film, it is good to form a groove of herring bone shape in the rotary body or the fixed body.
A dynamic pressure becomes high while the fluid dynamic bearing motor rotates at high speed. Therefore, in case of the low speed rotation, the possibility is high to rub between the rotary body and fixed body. Therefore, it is necessary to have the structure of generating a dynamic pressure in a low speed rotation. Moreover, wrap around and maintenance of the fluid are important to spread the dynamic pressure around the fluid dynamic bearing motor. And it need to reduce the size in correspondence to the miniaturization of an instrument.